O-rings are widely popular in the manufacturing of different machines. One of the most common materials that are used in the making of O-rings is elastomers. There are two types of elastomers that exist in the market and both can be used to make the O-rings: one is the Viton ® (FKM Fluoroelastomer) sheets and the other is EPDM rubber.
These rubbers polymers are known for their ability to get compounded at a low compression set. So, they tighten to the surface against which they are pasted. Both these elastomers can be stretched and are flexible to a great extent. They don’t break and you will often see them used as gaskets for pressure cookers and for making pumps, valves, and similar other items. But even though they have such similarities, there are numerous differences between these two elastomers. On one hand, Viton ® (FKM Fluoroelastomer) rubber is considered as a fluoro elastomer, while on the other hand, EPDM is considered as ethylene-propylene-diene-monomer. Without further ado, let’s take a look at some of the main differences between these two rubber polymers:
One of the biggest differences between Viton ® (FKM Fluoroelastomer) rubber and EPDM rubber is their chemical resistance. Viton ® (FKM Fluoroelastomer) rubber is resistant to some minerals and also edible oils like vegetable oil. In addition to these two items, this elastomer is also resistant to aromatic hydrocarbons, many alkalis, and gasoline.
EPDM rubber has poor resistance to some other items such as fuels, grease, and mineral oils. However, it is highly resistant to items like silicone oils, glycol based brake fluids, polar solvents like ketones, and hot water and steam.
There are some common items that both these polymers have good resistance to such as weather conditions, ozone, and oxygen.
Temperature is another factor that helps to understand the difference between these two elastomers. The temperature resistance of Viton ® (FKM Fluoroelastomer) rubber ranges from -20°C to 210°C. That is why it is mostly used for items that require a high temperature resistance. On the other hand, EPDM rubber has a temperature resistance that ranges from -45°C to 145°C. Although both the elastomers are widely used for items that need a high temperature resistance, EPDM rubber has a slight advantage over Viton ® (FKM Fluoroelastomer) rubber when it comes to working low temperature conditions. However, Viton ® (FKM Fluoroelastomer) rubber has an upper hand on EPDM rubber when the temperature condition required is more than 145°C.
Cost of the Elastomers
Now that you have an idea of the characteristics of the two elastomers, you would want to know what their price is and if they are readily available in the market. Yes, both EPDM rubber and Viton ® (FKM Fluoroelastomer) rubber are available. But Viton ® (FKM Fluoroelastomer) rubber is comparatively much more expensive than EPDM rubber. In fact, the former is almost eight times more expensive than what EPDM generally costs. However, there is one advantage that Vitron rubber will provide even if they are expensive. You will get them in a variety of sizes. Different machines may require different O-rings and if you are looking for a range of sizes, then Vitron rubber should be your first choice. EPDM rubber may be less expensive than Vitron but they are not available in such a wide range of sizes.
Applications of the Elastomers
Many people think that since both these elastomers are used in O-rings, they are similar in nature. But in reality, they are not. Since Viton ® (FKM Fluoroelastomer) polymer has a high chemical and oil resistance, it is widely used in chemical, food, and the petrochemical industries. These Vitron polymers consist of nitrile O-rings that are used in the industries mentioned above.
EPDM has a moderate chemical resistance and that is why it works best where steam applications are required. This rubber polymer is not used in industries that deal with petroleum solvents and agents.
So, if you are in a dilemma to choose between Vitron rubber and EPDM rubber, it will be best to understand their compatibility of the respective fluid that they are going to work in the required application. The temperature conditions along with the chemical resistance of the item will come into play when you decide between these two rubbers. Make sure you go through the details given above before choosing one for your project.